Smokers in Wales who spark up in their car while travelling with an under-18 passenger could soon face a £50 fine, according to the Welsh Government.
A six week consultation on plans to issue on-the-spot fines to drivers caught with a cigarette in their hand was launched today.
The Welsh Government says the ban would protect children from toxic second hand smoke.
"Some people light up in their cars without thinking and believe that opening the window will help disperse the smoke; however it simply blows back into the car," said Welsh First Minister Carwyn Jones.
"Children cannot escape from the toxic chemicals contained in second-hand smoke when travelling in vehicles."
The director of one of the UK's biggest e-cigarette companies has called warnings about health problems associated with the products are "baseless nonsense".
Charles Hamshaw-Thomas, legal and corporate affairs director at E-Lites, said:
""Study after study is showing that scaremongering that e-cigarettes are luring people into tobacco is baseless nonsense. The reverse is going on - smokers are switching into e-cigarettes as the way to reduce the harm from tobacco."
The use of electronic 'E-cigarettes' has tripled over the last two years, with over 2 million Britons now regularly smoking them.
Health charity ASH released figures showing a rise from 700,000 in 2012 to 2.1 million this year.
The group said two thirds of e-cigarette smokers still smoke normal cigarettes, while the remaining third were former smokers.
David Cameron is "minded to go ahead" with introducing plain packaging for cigarettes before next May's general election, Downing St has said.
At a media briefing this afternoon, the Prime Minister's spokesman said:
"The first thing to do is publish the draft regulations. We do have to consult on those in detail, partly to deal with the risk of future charges. Subject to that, we will certainly consider whether that is possible.
"The Prime Minister is minded to go ahead with this, subject to the consultation on detailed regulations," he added.
The tobacco industry has attacked the Government over the decision to pave the way for plain packaging for cigarettes in England.
Several companies said a review by Sir Cyril Chantler saying plain packs could improve public health was flawed.
A spokesman for British American Tobacco, whose brands include Pall Mall and Lucky Strikes, said the idea the plan would improve public health "defies logic".
Japan International Tobacco, the makers of Camel and Silk Cut, also pointed out that David Cameron has said the proposals involved "considerable legal uncertainty".
ITV News Deputy Political Editor Chris Ship has been speaking to Sir Cyril Chantler, the author of a review that concluded that plain cigarette packaging could contribute to a "modest but important reduction" in smoking rates.
Author of smoking study Sir Cyril Chantler tells us #plainpackaging is about "denormalising smoking in society"
The government said it will press ahead with plans to force tobacco firms to sell cigarettes in plain packets which would "very likely" improve public health.
Draft regulations to introduce plain packaging for cigarettes are to be published following the Sir Cyril Chantler review, health minister Jane Ellison said.
Ms Ellison said a short consultation will follow and details of when the changes will take place will be announced shortly which drew cries of "shame" from some MPs.
She said she wanted to move forward as swiftly as possible, explaining: "I am currently minded to proceed with introducing regulations to provide for standardised packaging.
"However, in order to ensure that decision is properly and fully informed I intend to publish the draft regulations so it is crystal clear what is intended".
International scientists conducting the new study looked at data on more than 2.5 million births and almost 250,000 hospital visits for asthma attacks.
Dr Jasper Been, from the University of Edinburgh, said:
Our research shows that smoking bans are an effective way to protect the health of our children.
These findings should help to accelerate the introduction of anti-smoking legislation in areas not currently protected.
Professor Aziz Sheikh, co-director of the university's Centre for Population Health Sciences, said:
This research has demonstrated the very considerable potential that smoke-free legislation offers to reduce pre-term births and childhood asthma attacks.
The many countries that are yet to enforce smoke-free legislation should in the light of these findings reconsider their positions on this important health policy question.
The findings are reported in the latest edition of The Lancet medical journal.